A novel resettable jar tool for use downhole in a borehole for enhancing the retrieval of stuck objects. The stuck object may be part of a tool string that includes the jar tool of this invention. The jar tool can withstand high temperature and other deleterious downhole conditions without significantly reducing the magnitude of the stored energy employed for actuating the jar tool.
The jar tool is resettable as many times as required to dislodge a stuck object by manipulating the operating wireline that allows electronic communication between apparatus connected to the bottom of the tool and the surface by an electrical conductor that extends through the entire jar tool. The jar includes a hammer, anvil and releasable latch device cooperatively interconnected to increase the safety of the tool and to deliver a powerful uphole thrust responsive to wireline tension.